Update bump version to 0.18.4 (840)

app/build.gradle

@@ -11,8 +11,8 @@ android {
         applicationId "org.schabi.newpipe"
         minSdkVersion 19
         targetSdkVersion 28
-        versionCode 830
-        versionName "0.18.3"
+        versionCode 840
+        versionName "0.18.4"
 
         testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
         vectorDrawables.useSupportLibrary = true